根据《招标投标法》规定，招标人和中标人应当自中标通知书发出之日起( )天内，根据招标文件和中标人的投标文件订立书面合同。

A．7

B．14

C．28

D．30

Some insects _____ the colour of their surroundings to protect themselves.  [ ]

A. take in

B. take off

C. take on

D. take out